Owen Vaughan from nChain released a paper Universal Blockchain Assets (UBA)
The blockchain is used for double-spend protection only, while the authorization of token transfers is performed off-chain. Due to the universality of our approach, it works in almost all blockchain settings
A novel protocol for issuing and transferring tokens across blockchains without the need of a trusted third party or cross-chain bridge. In our scheme, the blockchain is used for double-spend protection only, while the authorization of token transfers is performed off-chain. Due to the universality of our approach, it works in almost all blockchain settings. It can be implemented immediately on UTXO blockchains such as Bitcoin without modification, and on account-based blockchains such as Ethereum by introducing a smart contract that mimics the properties of a UTXO.
Protocol provide a proof-of-concept implementation of an NFT that is issued on Bitcoin, transferred to Ethereum, and then transferred back to Bitcoin. Our new approach means that users no longer need to be locked into one blockchain when issuing and transferring tokens. Current working implementations are for BSV and Ethereum it seems.
Whitepaper: https://nchain.com/wp-content/uploads/2024/05/Universal_Blockchain_Assets.pdf
